1. Field of the Invention
The present invention relates to a laminate-type piezoelectric element with a high durability, obtained by stacking ceramic layers and internal electrode layers, and a method of manufacturing the element.
2. Description of the Related Art
In the past, for example, there was a laminate-type piezoelectric element using a ceramic laminate with a partial electrode structure, wherein an outer peripheral part of each of internal electrode parts forming the internal electrodes layer is not exposed at a connecting area for connecting the external electrode (e.g. Japanese unexamined patent publication No. 2003-205511).
Further, in order to improve the reliability of electrical insulation at an outer peripheral area of the ceramic laminate, for example, there is a laminate-type piezoelectric element in which the outer peripheral part of the internal electrode part is not exposed at the outer peripheral area except for said connecting area in said ceramic laminate.
However, there is the following problem in said current laminate-type piezoelectric element. More specifically, there is a problem that stress, according to a piezoelectric displacement of said laminate-type piezoelectric element, concentrates at non-pole parts, wherein said internal electrode parts do not exist at the inside near outer peripheral parts, and displacement due to a piezoelectric effect does not occur.
On that account, there have been cases where cracks, etc. were caused between layers of said ceramic laminate, due to concentration of the stress, when the laminate-type piezoelectric element was used for a long period.
Therefore, it was not easy to obtain both of high performance and high durability in current laminate-type piezoelectric element.